Storage and retrieval machines are commonly used in material and inventory storage facilities for storing items in and retrieving the items from the facilities. Typical of such facilities are warehouses having storage racks of substantial height and width arranged along aisles in which the storage and retrieval machines travel on rails to various rack locations. Due to the need to have a highly efficient storage facility, the storage racks are designed to provide a maximum number of rack storage locations.
In another aspect of storage and retrieval machines, the machines are typically self-propelled by electric drive motors and provided with signals from a remote location to direct them to each rack location. Due to the complexity of the storage and retrieval machines and the overall storage and retrieval system, and to typical high duty usage of the machines, occasional breakdowns in the system result in the machines running out of control to an aisle end and impacting a mechanical stopping device. As a result of the impact, the machine may tip and therefore anti-tip devices are usually employed to prevent tipping.